1. Field of Invention
This invention relates generally to shower mirrors, specifically to a non-fogging shower mirror that employs heated shower water.
2. Background--Prior Art
Shower mirrors that do not fog in the presence of warm water vapor are known. Such mirrors use either a chemical coating on the surface of the mirror or a means of heating the mirror to keep it fog-free.
Those mirrors that use a chemical coating to prevent fogging are not entirely effective. Also the chemical coating eventually wears off, whereupon the mirror fogs as much as an untreated mirror.
Mirrors in which heat is used to keep the mirror fog free are numerous.
For example, my U.S. Pat. No. 4,836,668 (1989) shows a fog-free shower mirror that is heated by water diverted from the shower arm to the back of the mirror. While effective and successful, this mirror wastes a small quantity of water that drips out of the bottom of the mirror assembly after it heats the mirror. Also, the diverted water slightly reduces the pressure of water coming out of the showerhead.
U.S. Pat. No. 3,530,275 to Rust (1970) shows an electrically heated mirror. This arrangement is dangerous since it requires electrical lines to be near water. Also this mirror is expensive to build and operate.
U.S. Pat. No. 4,327,961 to Kladitis (1982) shows a mirror backed by a compartment that the user fills with warm water to keep the mirror fog-free. This mirror is cumbersome to use and is fog-free only temporarily since the warm water must be replenished periodically.
U.S. Pat. No. 4,556,298 to Gottlieb (1985) shows a non-fogging bathroom mirror. It employs water diverted from the shower pipe to a multiply bent tube attached to the rear of a metal mirror. The water heats the tube and the tube in turn heats the mirror. However this system is disadvantageous because the pipe must be soldered or otherwise joined in heat conducting relation to the mirror. This requires that the mirror be made of a solderable material, such as brass. This material and the soldering procedure are expensive and unreliable. Also, unless a very thick, heavy, or highly conductive mirror is used, the tube will heat the mirror generally only in the area covered by the tube, so that only this area (having a pattern corresponding to the tube) will be fog-free; the rest of the mirror will be fogged.
U.S. Pat. No. 4,557,003 to Jones (1985) shows a shower mirror in which an arm with joints and two internal water conduits is connected from the shower pipe to the mirror housing. Water flows through a supply conduit in the arm to a plenum behind the mirror to heat the mirror. Then it flows through a return conduit in the arm back to the shower pipe. This system has a disadvantage in that the entire arm, including its joints and conduits, must be sealed so as to accommodate the entire line pressure of the water line. This is difficult and expensive to accomplish while still enabling the arm to be flexible. Further, designing a sealed plenum that is strong enough to withstand line pressure yet thin enough to transfer heat is very difficult.